ON THE CONSTANCY OF COSMIC SPHERULE INFLUX DURING THE QUATERNARY

The influx rate of cosmic spherules can be measured on sediments of which the rate of deposition is known. It proved to be constant over long geological periods. Also, deposits of homogeneous composition in which the spherule concentration did not fluctuate appear to prove that the influx rate of cosmic spherules remained constant when the respective sediments had been laid down. Certain deep-sea cores are particularly suited for such an investigation. The deep-sea sediments from which the author has drawn his conclusions are of quaternary age.     

Chemical characteristics of dissolved organic nitrogen in an oligotrophic subtropical coastal ecosystem

Water samples were collected from rivers and estuarine environments within the Florida Coastal Everglades (FCE) ecosystem, USA, and ultrafiltered dissolved organic matter (UDOM; <0.7 μm, >1 kDa) was isolated for characterization of its source, bioavailability and diagenetic state. A combination of techniques, including ¹⁵N cross-polarization magic angle spinning nuclear magnetic resonance (¹⁵N CPMAS NMR) and X-ray photoelectron spectroscopy (XPS), were used to analyze the N components of UDOM. The concentrations and compositions of total hydrolysable amino acids (HAAs) were analyzed to estimate UDOM bioavailability and diagenetic state. Optical properties (UV-visible and fluorescence) and the stable isotope ratios of C and N were measured to assess the source and dynamics of UDOM. Spectroscopic analyses consistently showed that the major N species of UDOM are in amide form, but significant contributions of aromatic-N were also observed. XPS showed a very high pyridinic-N concentration in the FCE-UDOM (21.7 ± 2.7%) compared with those in other environments. The sources of this aromatic-N are unclear, but could include soot and charred materials from wild fires. Relatively high total HAA concentrations (4 ± 2% UDOC or 27 ± 4% UDON) are indicative of bioavailable components, and HAA compositions suggest FCE-UDOM has not undergone extensive diagenetic processing. These observations can be attributed to the low microbial activity and a continuous supply of fresh UDOM in this oligotrophic ecosystem. Marsh plants appear to be the dominant source of UDOM in freshwater regions of the FCE, whereas seagrasses and algae are the dominant sources of UDOM in Florida Bay. This study demonstrates the utility of a multi-technique and multi-proxy approach to advance our understanding of DON biogeochemistry.     

Reinhard Maack

Ohne Zusammenfassung

---

Reinhard Maack

     

Tree Species Composition in European Pristine Forests: Comparison of Stand Data to Model Predictions

The degree of general applicability across Europe currently achieved with several forest succession models is assessed, data needs and steps for further model development are identified and the role physiology based models can play in this process is evaluated. To this end, six forest succession models (DISCFORM, ForClim, FORSKA-M, GUESS, PICUS v1.2, SIERRA) are applied to simulate stand structure and species composition at 5 European pristine forest sites in different climatic regions. The models are initialized with site-specific soil information and driven with climate data from nearby weather stations. Predicted species composition and stand structure are compared to inventory data. Similarity and dissimilarity in the model results under current climatic conditions as well as the predicted responses to six climate change scenarios are discussed. All models produce good results in the prediction of the right tree functional types. In about half the cases, the dominating species are predicted correctly under the current climate. Where deviations occur, they often represent a shift of the species spectrum towards more drought tolerant species. Results for climate change scenarios indicate temperature driven changes in the alpine elevational vegetation belts at humid sites and a high sensitivity of forest composition and biomass of boreal and temperate deciduous forests to changes in precipitation as mediated by summer drought. Restricted generality of the models is found insofar as models originally developed for alpine conditions clearly perform better at alpine sites than at boreal sites, and vice versa. We conclude that both the models and the input data need to be improved before the models can be used for a robust evaluation of forest dynamics under climate change scenarios across Europe. Recommendations for model improvements, further model testing and the use of physiology based succession models are made.     

Anomalous strontium and lead isotope signatures in the off-rift Öræfajökull central volcano in south-east Iceland: Evidence for enriched endmember(s) of the Iceland mantle plume?

The currently active off-rift central volcano Öræfajökull in south-east Iceland sits unconformably on much older (10–12 Ma) and eroded crust. The composition of recent volcanics ranges from basalt to rhyolite, but the series is more sodic alkaline than the common rift zone tholeiitic suites. In this study we present Sr, Nd, Pb and O isotopic data for a suite of Öræfajökull samples. The complete suite shows typical mantle values for oxygen isotopes. The ⁸⁷Sr/⁸⁶Sr ratios (average of 15 SAMPLES=0.703702) of the modern Öræfajökull rocks (basalts as well as rhyolites) are much higher than observed so far for any other Icelandic rocks. The ¹⁴³Nd/¹⁴⁴Nd ratios (average=0.512947; n=15) are lower than for rift rocks, but similar to rocks of the off-rift Snæfellsnes volcanic zone. Furthermore, the Öræfajökull rocks are enriched in the ²⁰⁷Pb/²⁰⁴Pb and ²⁰⁸Pb/²⁰⁴Pb isotope ratios compared to Icelandic rift basalts. The enriched nature of the suite indicates that Öræfajökull samples a source component that has characteristics common with EM2 type mantle. Furthermore, it is concluded that the silicic rocks of Öræfajökull formed by fractional crystallization from mafic melts rather than by partial melting of older crust.     

Private property restitution: the geographical consequences of official government policies in Central and Eastern Europe

The restitution of private property has been a widespread and controversial part of the post-socialist transformation in Central and Eastern Europe, raising issues about social justice and the responsibilities of national governments for the actions of their predecessors. This paper reviews the implementation of the restitution process in the countries of the region and assesses the impact on the social and economic landscape. The policy has been most extensive in Germany and most controversial in Poland, and the impacts in these two countries are considered in detail. The results show that everywhere restitution has resulted in winners and losers, with some claimants having long-lost property returned, but too often at the cost of residents losing their homes. However, an important benefit, notably in Germany's New Bundesländer, has been the introduction of much-needed new investment into the urban fabric of towns and cities, although the landscape impacts elsewhere have been less significant. Nevertheless, throughout Central and Eastern Europe restitution policies have helped governments to come to terms with a difficult aspect of the past and move forward.     

Parasite findings in archeological remains: Diagnosis and interpretation

Paleoparasitology has contributed to resolving the debate about the peopling of the Americas and determining the antiquity of human parasite infection. Hookworm (Ancylostomidae) and whipworm (Trichuris trichiura) and other exclusive human intestinal parasites have been recorded in pre-Columbian America. These parasite species originated in pre-hominids and have accompanied humans across continents when people went out of Africa. However, for those human populations that crossed the Bering Land Bridge from Siberia to Alaska, cold climate conditions hampered parasite transmission. Alternative migration routes have been proposed to explain the presence of these parasites in pre-Columbian populations in the Americas. Other parasites were established in the New World long before humans entered the American continents.One such malady is Chagas disease. Chagas disease, caused by Trypanosoma cruzi, offers an example of how animals and humans have interacted in the past. Classical theory points to the origin and dispersion of human T. cruzi infection among Andean populations, starting with sedentary habits and animal domestication 6000 years ago. However, recent PCR results in mummified bodies outside the Andean region have challenged this theory. Pre-Columbian Brazilian mummies were found positive for T. cruzi infection, raising an alternative hypothesis on the antiquity of Chagas disease in the Americas. Paleoparasitology is a new tool to study past events, shedding light on human and other animal behavior, migration routes, diet, and other aspects of host–parasite environment evolution.